Natural attenuation of fatty acid methyl esters (FAME) in soil and groundwater

Fatty acid methyl esters (FAME) are a group of organic compounds that can be synthesized through the process of esterification of fatty acids with methanol. With the increasing use of FAME in biodiesel, there is interest in the fate and effects of FAME in the environment. Single FAME compounds are of low aqueous solubility, low volatility and low mobility but the mechanisms of autoxidation and hydrolysis may result in the generation of more mobile but equally biodegradable components. The FAME types that have been studied in the peer-reviewed literature do not appear to enhance the solubility of hydrocarbons. FAME are widely reported to be readily biodegradable under both aerobic and anaerobic conditions, although rates may vary from site to site. In the majority of studies, biodiesel FAME biodegradation occurred more rapidly than petroleum diesel biodegradation. At sites with limited electron acceptors and macronutrients, microorganisms that degrade FAME have the potential to deplete available electron acceptors and nutrients, resulting in an extended time for diesel biodegradation. As with other labile biofuels, anaerobic biodegradation of FAME may result in significant methane generation. Overall, natural attenuation would appear to be significant in controlling the fate, behaviour and potential risks posed by biodiesel.